The present invention relates to a laminated heat exchanger that may be employed in an evaporator or the like constituting the refrigeration cycle in an air conditioning system for vehicles, for instance, having an inflow port and an outflow port provided side-by-side at one side in the direction of the lamination.
The invention completed by the applicant of the present invention, which is disclosed in Japanese Unexamined Patent Publication No. H8-121988, achieves the prevention of freezing damage or corrosion of the tube elements or the communicating pipe which may occur in a laminated heat exchanger constituted by laminating tube elements each having a pair of tanks at one side and a groove portion formed between the tanks alternately with fins over a plurality of levels so that a communicating passage extends between the tanks in the direction of the lamination with the communicating pipe mounted at the communicating passage, when water is collected in the gap formed through defective brazing of the communicating pipe and the circumferential edges of the groove portions constituting the communicating passage. This invention is already in use.
According to this invention, each of the tube elements is provided with a pair of tanks and a U-shaped heat exchanging medium passage communicating between the pair of tanks and is constituted by bonding face-to-face a pair of formed plates. In one of the formed plates in the pair, a flange that is bent toward the non-bonding side is formed in order to increase the strength of the formed plate over the entire circumference at the edge portion of the brazing margin at the circumferential edges of the distended portion for passage formation and the distended portion for tank formation, whereas in the other formed plate, this flange and a brazing margin continuous to the flange are notched over the entire circumferential edge of the groove portion between the tanks. With this, in tube elements constituted by bonding these formed plates, only the groove portion at one of the formed plates comes in contact with the communicating pipe. Alternatively, one side relative to the center of the circumferential edge of the groove portion in each formed plate may be notched, and in tube elements constituted by bonding such formed plates, the communicating pipe comes in contact with alternate groove portions.
As a result, since a large opening is formed between the communicating pipe and the groove portions of the tube elements having the width over which the center of the circumferential edge of the groove portion at the formed plate is notched toward the front end of the formed plate or having the width over which one side relative to the center of the inside circumferential edge of groove portion of the formed plate notched toward the front end of the formed plate, drainage is improved to prevent water from collecting, so that a problem of collected water repeatedly freezing and melting to damage the tube element and the communicating pipe is eliminated. In addition, the problem of the tube element and the communicating pipe becoming corroded by the collected water, is avoided.
Now, laminated heat exchangers employing a communicating pipe include the type illustrated in FIGS. 12 and 13, in which a formed plate 100 and a flat plate 101 are bonded to each other at one side in the direction of the lamination, a distribution plate 102 is further bonded to the flat plate 101 to form an inflow passage 103 and an outflow passage 104 and one end of a communicating pipe 106 is inserted and fitted in a hole 105 formed in the flat plate 101 to allow a heat exchanging medium to flow in to a specific tank through the inflow passage 103. In this heat exchanger, in order to perform brazing of the flat plate 101 and the communicating pipe 106 in a reliable manner, a flange 107 is formed at the circumferential edge of the hole 105 of the flat plate 101 extending toward the non-bonding side that is not bonded to the formed plate 100.
If the formed plate 100, which is bonded to the flat plate 101 in the laminated heat exchanger, is structured identically to a formed plate in the prior art described earlier, since a bonding margin 109 that contains a flange 110 of the formed plate 100 is bonded to a portion of the flat plate 101 which is in close proximity to the flange 107 at one end of the groove portion 108, there are potential problems that may occur in the event of defective brazing, in that a triangular gap A which is not filled with the brazing material is formed between the formed plate 100, the flat plate 101 and the communicating pipe 106 as illustrated in FIG. 14. This results in water such as the drain water collecting in the gap A and, through a process of repeated freezing and melting, damaging the tube element 111 constituted of the formed plate 100 and the flat plate 101 or the communicating pipe 106, and in the collected water corroding the tube element 111 or the communicating pipe 106.